I have a main.html file in folder discord (discord/main.html). When in the main file i put <a href="/discord/main.html">Link</a> i get an error: Cannot GET /discord/main.html. So how is possible to link to discord/main.html ?
Wait nvm, solved! 
For people who don’t know how to do this (I know you have solved it yourself). Just make sure that your folder is in views. Example: views/discord/index.html can be accessed from https://yorprojectname.glitch.me/discord/index.html
Ta da! 